<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="app">
        hello
    </div>
    <script>
        let data = {
            msg: '123',
            count: 10
        }

        let vm = new Proxy(data, {
            get (target, key) {
                console.log('get', key, target[key])
                return target[key]
            },
            set (target, key, newVal) {
                console.log('set', key, newVal)
                if (target[key] === newVal) {
                    return
                }
                target[key] = newVal
            }
        });
    </script>
</body>
</html>